Problem: If $x \boxdot y = 3x-4$ and $x \bigtriangleup y = x-8y$, find $(6 \bigtriangleup 2) \boxdot -6$.
First, find $6 \bigtriangleup 2$ $ 6 \bigtriangleup 2 = 6-(8)(2)$ $ \hphantom{6 \bigtriangleup 2} = -10$ Now, find $-10 \boxdot -6$ $ -10 \boxdot -6 = (3)(-10)-4$ $ \hphantom{-10 \boxdot -6} = -34$.